It is an unfortunate fact that terrorists often attempt to influence the course of political events through the use of violence. One infamous means for implementing these violent actions is by strategically placing bombs where they will cause the greatest devastation and have the greatest political impact. Indeed, bombs almost seem to be a terrorist weapon of choice. As is well known, terrorist targets are typically chosen on the basis of their vulnerability to such attack and are frequently, if not purposefully, selected without regard for human life. Crowds of people can, therefore, be an attractive terrorist target due to the intense public reaction that mass murder will provoke. Further, vehicles are attractive targets because they are compact and will almost always contain people when they are being operated. Aircraft effectively combine these attractions.
Despite extremely tight security procedures, and the use of sophisticated explosive detecting electronic equipment, it happens that bombs have still found their way aboard aircraft. Typically, it has happened that bombs have been found hidden in passenger luggage or in parcels which are stored and carried in the cargo compartment of an aircraft. There is, of course, a limit to the size of bomb which can be relatively easily detected. Consequently, one strategy is to recognize that small bombs may not always be detected and then plan on ways in which to reduce the damage which can be caused by a small bomb.
Within the airline industry it is a standard practice to compartmentalize the cargo which is to be carried on board the larger aircraft. This is done by separating the cargo into separate units and placing these units of cargo into individual containers which are commonly referred to as unit load devices (ULDs). Because of regulatory requirements, as well as practical considerations, the shape, size and weight of a ULD for each type aircraft has been pretty much standardized. Consequently, in order to design a ULD which will meet the standard requirements of the industry, and still effectively withstand a substantially large blast from an explosion in the cargo held within the ULD, these limitations need to be considered.
Typically, ULDs are shaped as boxes which can include appropriately sloped surfaces that conform the ULD to the aircraft's fuselage when the ULD is placed in the aircraft's cargo compartment. Essentially, the container is made of several panels which are joined together to form the ULD. Additionally, each ULD has a door or an access hatch which allows it to be opened for placing cargo in the ULD or for removing cargo from the ULD.
From studies which have been conducted to determine how a standard ULD will react to an internal explosion, it is known that the panels which form the container of the ULD will tend to bulge outwardly from the blast. Further, it is known that panels are relatively strong in structurally resisting the tensile stresses which are directed in the plane of the panel. Stated differently, panels are relatively effective in resisting rupture. On the other hand, stress analysis shows that the highest stress concentrations which result from an explosion within the ULD occur at the joints and around the door or hatch which covers the opening into the ULD. One obvious means for providing a hardened ULD is to simply add more material at the points where the highest stress concentrations occur. It is preferable, however, to avoid this additional weight. Instead, though some reinforcing material may be selectively used, the present invention recognizes that a proper design for the components of the ULD, and a proper design for the interaction of these components, are effective in helping solve the presently existing problems.
In light of the above it is an object of the present invention to provide a hardened load carrying device for use in transporting cargo on aircraft which is able to resist internal blasts without rupturing. Another object of the present invention is to provide a hardened load carrying device which selectively incorporates reinforcing material at the points where an internal explosion generates the highest stress concentrations in the device. Yet another object of the present invention is to provide a hardened load carrying device which meets the regulatory standards for the use of such devices in air transport operations. Still another object of the present invention is to provide a hardened load carrying device which allows relative easy access into the device through an opening which can be effectively covered without compromising the efficacy of the device. Another object of the present invention is to provide a hardened load carrying device which is easy to use, relatively easy to manufacture, and comparatively cost effective.